Burn affected by Air moisture?

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Status
Not open for further replies.

Redbear86

Member
Jun 30, 2011
149
SE Idaho
I know its incredibly technical and maybe ridiculous on grand scale of things, but would you not get a better burn if the air inside your house (or outside if your using OAK) was drier? I know, I have too much time on my hands to think of this!
 
Redbear86 said:
I know its incredibly technical and maybe ridiculous on grand scale of things, but would you not get a better burn if the air inside your house (or outside if your using OAK) was drier? I know, I have too much time on my hands to think of this!
not totally true, esp. if you have a newer EPA stove with an outside air kit installed (OAK). And furthermore, if it was really that big of a difference to have super dry air in your house for better burns, you would suffer drastically on dry skin, so I'll stick with some humidity, not too much, just around 30 to 35% in the winter.....and that isn't easy to stay that moist cause we heat exclusively with wood!
 
Under controlled conditions there is prob a difference but in the real world I doubt it is anything you can feel seat of the pants.
 
The air inside your house came from outside the house, and it gets exchanged many times per day. Both will have basically the same amount of water (absolute humidity) per unit volume, but the warmer air in the house will now have a higher capacity to absorb water, so the relative humidity will be lower than the outside air.

http://en.wikipedia.org/wiki/Humidity

I don't think it makes a measurable difference. Good thing, because you really have no control over the amount of water in the outside air. ;-)
 
Like I said before i don't think it would make a measurable difference, people who burn with wood usually don't have a problem with it being too "moist" inside, but more specifically people who put a big 'ol steamer on their stove, wouldn't the moisture more times than not get pulled back into the stove fairly quickly? The air in your flue can condensate creating creosote problems if its not kept fairly hot (much hotter than the air above your stove inside the house) so the saturated air above your stove would cool quicker and the moist air would "fall" back to the stove's level being sucked into the fire again. I know a steamer makes a difference in air moisture having grown up in an old farm house with a couple wood stoves. Another point some one could make is if i remember correctly from physics but doesn't air with more moisture in have the potential to "hold" more heat? I know this is a silly thing to discuss, but the Packer game is over and i'm kinda bored, thanks you for entertaining my crazy rationalities!
 
Warm air will hold more heat than cold air. However, you can have the same relative humidity in either and yes, you will feel warmer with the higher humidity....up to a point and the warmer air will not hold the heat longer. As for that slightly (very slight) higher moisture air having a difference on the fire, I do not see how that could be. Remember that the wood you put into the stove has moisture in it already.

How could one be bored after watching another Packer game?!!
 
On mild, muggy humid days I seem to have more issues getting a good draft and fire going than crisp, clear, cold days.

Not sure if it's pressure, humidity, temp differences in the chimney vs. outside air or what. I have an OAK for my little stove - you'd think the humidity outside wouldn't have that much affect, since I'd imagine over all it's less than the moisture content of the wood itself - no?
 
jonwright said:
... you'd think the humidity outside wouldn't have that much affect, since I'd imagine over all it's less than the moisture content of the wood itself - no?

Absolutely... at whole lot less.

Even at 100% RH a cubic foot of outside air (30ºF) is only holding a few tenths of a gram of water. At 50% RH the same amount of air at that temp has maybe a drop of water per cubic foot. OTOH ten pounds of good, seasoned firewood has about two pounds of water in it.

And that's only the tip of the iceberg. Burning wood to completion creates about .54 pounds of extra water for every pound of dry wood fiber burned. Burning eight pounds of wood fiber in that ten-pound split makes 4.3 pounds of extra water above and beyond the initial water present in the wood. So, ten pounds of seasoned wood sends about this much water up the flue:

- 2 pounds of water from the excess water in the wood
- 4.3 pounds of water as a product of the combustion of 8 pounds of wood fiber
- 1 ounce of water from roughly 600 cubic feet of intake air needed to combust 8 pounds of wood fiber.
 
I'd have to say no, it doesn't affect a burn because the water in the air is already in the vapor phase so doesn't require and heat to vaporize.
 
Have no problem burning here with damp air, and when I say damp, we can go for a month or more at 80 - 90% humidity this time of year....... ;-)
 
Hey woodchip, I hear you have lots of water surrounding your area. Maybe that is why... :)
 
Those are some surprising numbers Batten- I had no idea wood combustion created so much moisture
 
Redbear86 said:
Those are some surprising numbers Batten- I had no idea wood combustion created so much moisture
Your burning carbohydrates in there, just like you and me. We breathe moisture, they breath moisture. :coolsmile:
 
Status
Not open for further replies.